Art medium



United States, Patent 3,263,605 ART MEDIUM Arthur L. Fry, North St. Paul, Minn., assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware No Drawing. Filed Oct. 11, 1963, Ser. No. 315,688

7 Claims. (Cl. 101-170) This invention relates to the field of art and is especially concerned with a sheet product which is highly useful in the preparation of plates for both relief and intaglio printing.

It has long been common for students and artists to employ conventional battleship linoleum as a medium forpreparing plates to be used in relief printing. A design is applied to the linoleum in mirror image of the form desired and the unwanted areas cut or goutged away. The relief area remaining after this operation is inked and the plate, preferably adhered to a rigid support to prevent flexing which might crack the design, is forced against the surface to be printed. The inking and printing operation is then repeated, as desired. Linoleum is inherently hard, brittle, and temperature-sensitive, characteristics which become worse as it ages. As a result it is extremely difficult to create fine lines in relief, particularly on a plate that is to be used repeatedly. Because of linoleums lack of resilience, it is necessary to apply heavy pressure in order to insure uniform contact with the surface being printed; this in turn often ruins a plate. Linoleum is not easy to cut, and it is necessary to sharpen the tools very frequently. Even then, most young students are unable to do satisfactory work on linoleum, often ruining their projects and/or injuring themselves.

Because of linoleums deficiencies, grade school artists usually work with other printing media. Vegetables, such as potatoes or carrots, are often used, but have obvious limitations, e.g., as to size, durability, and permanence. Likewise, strips or designs have been cut from old inner tubes, but such materials are rubbery and difiicult to work with, resulting in distortion during both preparation and printing, and coresponding lack of detail in the finished print. Attempts have also been made to employ such rubber sheet material as sandblast stencil, e.g., of the type disclosed in Wartha U.S. Patent No. 2,251,647. Although more satisfactory than either inner tubes or linoleum, sandbtlast stencils have also been difiicult to cut with art tools without having the cutting tool chatter or leave ragged edges. Resistance to cutting is extremely high, making it extremely diflicult for young artists to produce consistently good results. Sandblast stencils suffer from the additional drawback that they are watersensit-ive, thereby making it impractical to use many of the water-based inks which otherwise lend themselves to school art practices.

Prior to my invention intaglio printing has been done only by comparative experts. Intaglio plates have been prepared either by acid-etching metals such as copper, steel or zinc, or by mechanically engraving metal or hard plastic sheets. The printing plate is covered with ink, which flows into the depressions in the surface of the plate; the raised surface is then wiped free of ink and a specially prepared SOtft conformable paper or other sheet material is placed over the surface of the plate. A resilient felt blanket or soft rubber roller on a high pressure press is used to force the paper against the plate and into contact with the ink contained in the depressions.

I have now devised a novel art medium which can be stored for a year or more without loss of its desirable attributes. This product is a highly superior replacement for all common hand crafted forms of relief printing plates known to me; in addition, it provides-for the first time insofar as I am aware-a simple, resilient flexible sheet which can be used in intaglio printing.

My novel art medium is a simple, convenient, easy to work with, versatile sheet material which is capable of repeated use. A pencil or charcoal design drawn by the student in the form in which it is to be printed may be directly transferred to the face of my novel sheet material, which is thereafter cut to the desired configuration. My sheet material is flexible, and may be adhered either to a rigid block, a roll, or to such supports as paper or cardboard. It may be cut into strips or pieces for use in forming intricate designs, thereby making possible essentially complete utilization of the material itself. Intaglio plates may be prepared, the resilient nature of this art medium making it possible to dispense with resilient supports, high pressure presses, and specially prepared papers or fabrics. Because this product is easily cut, it is safer for children to use, as well as being more appealing to adults. Tools used to prepare the surface need be sharpened only upon rare occasions. Even such simple tools as a pair of scissors, a paper clip, or a pin, may be used to create interesting and effective designs.

In accordance with my invention I employ a selfsupporting amorphous, compliant, firm, extensible smooth thermoplastic sheet which is rfrom about .025 to about .075 inch thick, coated over one surface with an aggressive adhesive, preferably a normally tacky and pressure-sensitive adhesive. The sheet comprises a polymer binder and an insoluble finely divided particulate filler. The binder is made up of from about 10 to 60 parts of readily extensible, Waxy, low density solid branched thermoplastic ethylene polymer, 5 to 76 parts of a soft, weak, flexible, resilient elastomer such as a stereospecific polybutadiene, and from 0-50 parts of a tough strong, flexible elastomer which can be formed per se into a smooth sheet, e.g., natural rubber.

The filler constitutes from about to about the total volume of the sheet, the exact quantity for a given binder system being selected so that it is sufiicient to keep the sheet from blocking but insufiicient to permit the sheet to break when it is bent back sharply against itself. It is important that this sheet material be substantially tree from any tendency to block, both to permit material which has been cut or gouged from the printing medium to be readily removed and to prevent the sides of narrow incised grooves from healing during printing. A simple blocking test involve-s placing one sheet of material on top of another and leaving the two at room temperature overnight; if there is any substantial tendency for the two sheets to stick together, blocking is regarded as excessive.

Because my novel art medium is extensible, it is desirable that it be adhered to a dimensionally stable support, e.g., metal, wood, paper, or cardboard. Accordingly, it is important that the adhesive be comparatively aggressive. It is also desirable that a continuous primer layer be present between the adhesive and the back of the 3 sheet to insure retention of optimum adhesion. For ease in use, a pressure-sensitive adhesive is desirably protected with a readily removable liner, especially a silicone-treated paper.

My invention will now be described by means of certain specific illustrative but non-limitative examples.

Example I To an 84-inch rubber mill heated to a temperature of 235 F. and set at a nip spacing of approximately 100 mils were added 33.3 lbs. of pelletized DFD 3300 (branched polyethylene having a density of 0.918, an average melt index of 3.5, and an average molecular weight of 20,000, sold by Union Carbide). In approximately 30 seconds, when the polyethylene had softened and stuck to the roll, the following finely divided particulate fillers were slowly and individually added: 25 lbs. of Silene EF (a reinforcing silica), 25 lbs. of Celite 165$ (diatomaceous earth) and 25 lbs. of ASP 103 (aluminum silicate in the form of hexagonal platelets). When these fillers had been thoroughly dispersed and wetted by the polyethylene, the nip of the mill was opened to about inch and the following materials added: 8.3 lbs. of Solka- Floc BW100 (a bleached short fiber cellulose), 11.7 lbs. of white factice (vulcanized vegetable oil), 1.6 lbs. of stearic acid, and .834 lb. of Agerite Resin D (a polymerized trimethyl dihydroquinoline antioxidant). When all the ingredients had been dispersed in and wetted by the polyethylene, 16.8 lbs. of smoked sheet rubber and 16.8 lbs. of Ameripol CB (a stereospecific cis-l,4- polybutadiene rubber having an average Mooney viscosity of 41.2, obtainable from Goodrich Gulf) were added simultaneously and the batch cut and blended to obtain a homogeneous mixture. The batch, or mill base, was then removed from the mill in pieces about /2 x 1 x 3'. Total time on the mill was about 35 minutes; alternatively the batch may be prepared on a Banbury, in about the time.

The dispersed mill base was preheated to 270-290 F. on a rubber mill and then calendered at 230240 F. to form a smooth .050 inch sheet about 250 yards long. A coating of Pliolite 160 (33:67 butadiene:styrene copolymer latex, sold by Goodyear Tire & Rubber Co.) was next applied to one surface of the calendered sheet backing in an amount sufficient to leave 10 grains of solid material per 24 square inches. The coating was dried in a 200 F. forced air convection oven, and the finished coated material then wound upon itself in roll form.

To the coated side of the calendered sheet was next applied a heptane solution of pressure-sensitive adhesive composition having the following ingredients (parts by weight):

Rubbery polyisobutylene (such as Vistanex B120) 100 Polybutene rubber (such as Indopol H300) 70 Pure hydrocarbon terpene tackifier resin (such as Piccolyte S85) 45 Rosin ester tackifier resin (such as Hercolyn) 30 Di-tert.-amyl hydroquinone antioxidant (such as Santovar A) 1.1

The coated sheet was dried by passing it through an oven to eliminate the solvent. At the oven exit a 40-lb. silicone-treated paper liner was squeeze roll-laminated to the adhesive-coated sheet and the completed article wound convolutely upon itself in roll form. Thereafter the roll was cut to sheets of convenient size, e.g., 8 /2" x 11", 22" x 30", etc.

The product of this example was easily cut with conventional linoleum cutting tools and stencil knives, the line of cut being clean and sharp. It was also readily cut into narrow strips with a pair of scissors, and the strips thereafter bent to complex curves or such shapes as the artist desired. The product was sufficiently resilient that intaglio plates made therefrom functioned on a simple roller press to produce excellent prints, and yet it was sufficiently firm that the printed sheet showed clean, sharp lines. The surface was readily receptive to waterbased inks, and hence the product was especially attractive for use With young grade school artists. Several thousand prints can be typically made from a relief plate. Normally 25 or more copies can be printed from even delicate intaglio plates without significant loss of detail. Plates can either be stored for future use, or, if desired, the individualstrips can be removed and employed in still further designs. The flexible nature of the product makes it possible to use cardboard as a backing, there being no danger of plate breakage or cracking upon bending. The aggressive pressure-sensitive adhesive holds the block or strips firmly in place.

Based on the specific gravity of the various binder and filler components, it was calculated that the filler constituted approximately 45% of the total volume of the sheet itself. Although the filler system employed in this example is fairly complex, and although it is preferred, many variations and simplifications can be made. For example, the entire filler system can be satisfactorily replaced with diatomaceous earth or an Attapulgus clay. Other fillers, e.g., calcium carbonate may also be used. In general, however, the filler system employed in this example provides a combination of receptivity to waterbased inks, millability, strength, and ease in cutting.

Example II A mill base was prepared in the manner described in Example I, from the following components, the figures indicating parts by weight:

DFD 3300 25 Silene EF 2.7 Celite 2.7

ASP 103 2.7 Solka-Floc BWlOO 0.9

White factice 1.2 Stearic acid 1.6 Agerite Resin D .8 Ameripol CB 25 This composition, which contained about 11% filler by volume, was slightly sticky but was milled, calendered to form a sheet, primed, and adhesive-coated as in Example I. The finished product showed excellent flexibility, ink receptivity, and was readily cut.

A conventional rubber mill can be employed without any particular criticality as to the milling time provided that the filler content of the mill base is at least about A the total volume and the temperature does not exceed about 240 F. If, of course, a Banbury is employed, or if the product is extruded, a lesser degree of filler will suflice. It has been found, however, that the sheet should contain at least about filler if it is to be readily cut by conventional printmaking tools. The quantity of filler should, however, the further adjusted so that, for those binder compositions which would otherwise tend to stick and block, the filler content is sufiicient to prevent such as occurrence. In general, increasing the amount of either the polybutadiene (or other soft, Weak, flexible elastomeric equivalent), e.g., to 70% or more, or the natural rubber (or other tough, strong, flexible elastomeric equivalent), e.g., to 40% or more, increases the tendency toward stickiness and blocking. Hence, in such compositions, it is generally preferred to have a filler content on the order of 50% or more by volume.

Example III A mill base was prepared, in the manner described in Example I, from the following components, the figures indicating parts by weight:

Other tough soft resilient elastomeric polymers which may be used in place of the Ameripol OB include chlorosulfonated polyethylene (e.g.,. Hypalon '20), polyisobutylene, rubbery polyvinyl ethers (e.g., polyvinyl ethyl ether or polyvinyl isobutyl ether), ethylene:acrylate ester copolymers (e.g., Bakelite DP DB), ethylene: propylene copolymers, etc. I have likewise found that for natural rubber I may substitute a low gel nitrile rubber having a Mooney viscosity in the range of 20-40, or calendering grades of either styrenezbutadiene or neoprene rubbers. Blends of equivalent materials may, of course, also be employed.

I am aware that certain of the compositions employed as the base for my novel art product are disclosed in Latham US. Patent No. 2,3 69,471, where they are broadly suggested for myriad uses. The patentee does not contemplate art products, nor would many of the products he discloses be adaptable to such use.

What I claim is:

1. For use in art work, a novel printing sheet material which can be stored at room temperature for a year or more without impairment of its function, and which can be adhered to a suit-able support, readily and cleanly cut to a desired contour or shape with a linoleum cutter, stencil knife, or scissors, and thereafter used in either re- DFD 3300" 3-3.3 Silene EF 5O Celite 16 5s 50 5 ASP 103 50 Solka Floc BWlOO 16.6 White factice 23.4 Stearic acid 1.6 Agerite Resin D .8 Ameripol OB 6.7 Smoked sheet 26.6

This composition, which contained about 62% filler by volume, was readily processable. The finished product was easy to cut and readily Wet by water-based printing inks, but showed a slight tendency to block. It was, however, judged acceptable.

The amount of filler can be increased to the volume ofthe composition, although there is an increasing tendency for the finished product to become excessively bri=ttle.

The following tabulated examples show the effect of varying the ratio of the three major binder components while maintaining a constant filler content of 45% by volume, as in Example I.

BINDER COMPOSITION Percent Percent Smoked Example Ameripol D FD Sheet 0 omments IV 70 0 Slightly soft but generally entirely satisfactory. V 20 60 20 Slightly tendency to crack when bent sharply; otherwise satisfactory. VI 10 50 40 Slightly rubbery but generally satisfactory. VII 30 35 Do. VIII 70 20 10 Processable on Banbury; finished product satisfactory.

The preceding examples illustrate the general range of compositions which I presently prefer in the practice of my invention. The amount of Ameripol GB in the binder can be reduced to about 5%, provided that the amount of smoked rubber is on the order of 50% and that the sheet contains at least about /2 filler by volume. The amount of DFD 3300 in the binder can be reduced to about 10%, provided that the sheet contains on the order of a least Ameripol CB.

Generally speaking, a product containing too little polyethylene is hard to cut, tending to be rubbery or sticky; too much polyethylene results in a product which breaks when bent sharply back on itself. If too little polybutadiene is present, the finished product is rubbery and tough or gummy; too much polybutadiene makes the mill base too sticky to process readily, and the final product blocks or is too rubbery. As noted, smoked sheet may be eliminated altogether if sufiicient polybutadiene is present; too much smoked sheet causes the finished product to be tough, rubbery, and hard to cut.

I have found that certain substitutions may be made for the individual binder components described in the preceding examples without dcleteriously affecting the quality of the finished product. F or example, ethylene polymers other than the DFD 3300" disclosed also function satisfactorily. Branched polyethylenes having a melt index of less than 300 have been found generally suitable, although the products having a high melt index tend to be excessively sticky. Likewise, ethylene may be copolymerized with vinyl esters such as vinyl acetate (e.g., Elvax 250, a 72:28 ethylenezvinyl acetate copolymer) or acrylate esters (e.g., Bakelite D P-DB, an ethylenezethyl acrylate copolymer). If desired, blends of Waxy ethylene polymers may be employed.

lief or intaglio printing, said sheet material comprising in combination:

a self-supporting, amorphous, compliant, firm, extensible smooth thermoplastic layer on the order of .050 inch thick consisting essentially of a binder comprising a homogeneous blend of parts by weight of 10-60 parts of readily extensible waxy, low

density, solid branched thermoplastic ethylene polymer,

575 parts of soft, weak, flexible resilient elasto-mer,

0-50 parts of tough, strong, flexible elastomer which can be formed into a smooth sheet, and

insoluble finely divided particulate filler, constituting from about to about /3 the volume of said layer, said tfiller further being present in amount sufiicient to keep said layer from blocking but insuflicient to permit said layer to break when bent back sharply against itself, and

an adhesive coated over one face of said layer.

2. For use in art work, a novel printing sheet material which can be stored at room temperature for a year or more without impairment of its function, and which can be adhered to a suit-able support, readily and cleanly cut to a desired contour or shape with a linoleum cutter, stencil knife, or scissors, and thereafter used in either relief or intaglio printing, said sheet material comprising in combination:

a self-supporting, amorphous, compliant, firm, extensible smooth thermoplastic layer onthe order of .050 inch thick consisting essentially of a binder comprising a homogeneous blend of 100 parts by weight of 10-60 parts of a branched polyethylene having a density of about 0.92 and a melt index of less than 300,

575 parts of a stereospecific cis-l,4-polybutadiene rubber having a Mooney viscosity in the range of 25-55,

-50 parts of smoked sheet natural rubber,

and

insoluble finely divided particulate filler, constituting from about to about /3 the volume of said layer, said filler further being present in amount sufficient to keep said layer from blocking but insufficient to permit said layer to break when bent back sharply against itself,

a continuous primer film coated on one face of said layer,

an aggressive normally tacky and pressure-sensitive adhesive adhered to said primer film, and

a release liner applied over said adhesive.

3. F or use in art work, a novel printing sheet material which can be stored at room temperature for a year or more without impairment of its function, and which can be adhered to a suitable support, readily and cleanly cut to a desired contour or shape with a linoleum cutter, stencil knife, or scissors, and thereafter used in either relief or intaglio printing, said sheet material comprising in combination:

a self-supporting, amorphous, compliant, firm, extensible smooth thermoplastic layer on the order of .050 inch thick consisting essentially of a binder comprising a homogeneous blend of 100 parts by weight of 10-60 pants of a readily extensible waxy, low

density solid branched thermoplastic ethylene polymer, selected from the class consisting of low density polyethylene, ethylenewinyl acetate copolymers, and ethylene:acrylate ester polymers, and blends thereof,

5-75 parts of a relatively tough, soft, resilient elastomeric polymer selected from the class consisting of stereospecific cis-1,4-polybutadiene rubber, chlorosulfonated polyethylene, polyisobutylene, rubbery polyvinyl ethers, ethylenezacrylate ester polymers, ethylene:pro-pylene polymers, and blends thereof,

0-50 parts of a linear unsaturated flexible rubber capable of forming a smooth sheet selected from the class consisting of natural rubber, low gel nitr-ile rubber having a Mooney viscosity in the range of 20-40, calendering grades of styrenezbutadiene rubber, calendering grade neoprene, and blends thereof, and

insoluble particulate filler constituting from to of the volume of said layer in amount sufficient to keep said layer from blocking but insufficient to permit said layer to break when bent back sharply against itself,

an aggressive normally tacky and pressure-sensitive adhesive adhered over one face of said layer, and

a release liner applied over said adhesive.

4. For use in art work, a novel printing sheet material which can be stored at room temperature for a year or more without impairment of its function, and which can be adhered to a suitable support, readily and cleanly cut to a desired contour or shape with a linoleum cutter, stencil knife, or scissors, and thereafter used in either relief or intaglio printing, said sheet material comprising in combination:

a self-supporting, amorphous, compliant, firm, extensible smooth thermoplastic layer on the order of .050 inch thick consisting essentially of a binder comprising a homogeneous blend of parts by weight of 10-60 parts of a branched polyethylene having a density of about 0.92 and a melt index of less than 300,

5-75 parts of a stereospecific cis-1,4-polybutadiene rubber having a Mooney viscosity in the range of 25-55,

0-50 parts of smoked sheet natural rubber,

and

insoluble particulate filler constituting from about A to about of the volume of said layer in amount sufiicient to keep said layer from blacking but insufficient to permit said layer to break when bent back sharply against itself,

an aggressive normally tacky and pressure-sensitive adhesive layer adhered over one face of said layer, and

a release liner applied over said adhesive.

5. For use in art work, a novel printing sheet material which can be stored at room temperature for a year or more Without impairment of its function, and which can be adhered to a suitable support, readily and cleanly cut to a desired contour or shape with a linoleum cutter, stencil knife, or scissors, and thereafter used in either relief or intaglio printing, said sheet material comprising in combination:

a self-supporting, amorphous, compliant, firm, extensible smooth thermoplastic layer on the order of .050 inch thick consisting essentially of a binder comprising a homogeneous blend of 100 parts by weight of 50-60 parts of a branched polyethylene having a density of about 0.92 and a melt index of less than 300,

5-75 parts of a stereospecific cis-l,4-polybutadiene rubber having a Mooney viscosity in the range of 25-55,

0-50 parts of smoked sheet natural rubber,

and

insoluble particulate filler constituting from about A to about /3 of the volume of said layer in amount sufiicient to keep said layer from blocking but insufficient to permit said layer to break when bent back sharply against itself,

a continuous coating of a flexible butadiene:styrene copolymer bonded to one face of said layer,

an aggressive normally tacky and pressure-sensitive adhesive layer adhered to said coating, and

a release liner applied over said adhesive.

6. A method of intaglio printing comprising cutting to intaglio configuration a self-supporting, amorphous firm, compliant, extensible smooth, non-blocking thermoplastic sheet on the order of .050 inch thick, said sheet comprising a homogeneous blend of 100 parts by weight of a binder consisting essentially of 10-60 parts of readily extensible, waxy, low density solid branched thermoplastic ethylene polymer, 5-75 parts of soft, Weak, flexible resilient elastomer, and 0-50 parts of tough, strong, flexible elastomer which can be formed into a smooth sheet, said sheet also containing finely divided particulate filler by volume, said filler further being present in an amount suificient to keep said sheet from blocking but insufficient to permit said sheet to break when bent back sharply against itself; adhering the intaglio-configured sheet material to a dimensionally stable support; inking the thusformed intaglio plate; removing the excess ink from the relief areas while retaining it in the depressions; and forcing said plate against the sheet to be printed, said plate compressing sufliciently to permit said sheet to contact said ink.

7. A novel printing plate comprising a suitably configured resilient sheet material having relief areas defining a design, said sheet material comprising:

compliant, firm, extensible smooth thermoplastic material on the order of .050 inch thick consisting essentially of a binder comprising a homogeneous blend of 100 parts by weight of 10-60 parts of readily extensible, waxy, low

density solid branched thermoplastic ethylene polymer,

5-75 parts of soft, weak, flexible resilient elastomer,

0-50 parts of tough, strong, flexible elastomer which can be formed into a smooth sheet, and

insoluble finely divided particulate filler, constituting from about to about /3 the volume of said material, said filler further being present in amount sufficient to keep said sheet material from blocking but insufficient to permit said sheet material to break when bent back sharply against itself.

References Cited by the Examiner UNITED STATES PATENTS 15 DAVID KLEIN, Primary Examiner. 

1. FOR USE IN ART WORK, A NOVEL PRINTING SHEET MATERIAL WHICH CAN BE STORED AT ROOM TEMPERATURE FOR A YEAR OR MORE WITHOUT IMPAIRMENT OF ITS FUNCTION, AND WHICH CAN BE ADHERED TO A SUITABLE SUPPORT, READILY AND CLEANLY CUT TO A DESIRED CONTOUR OR SHAPE WITH A LINOLEUM CUTTER, STENCIL KINFE, OR SCISSORS, AND THEREAFTER USED IN EITHER RELIEF OR INTAGLIO PRINTING, SAID SHEET MATERIAL COMPRISING IN COMBINATION: A SELF-SUPPORTING, AMORPHOUS, COMPLIANT, FIRM, EXTENSIBLE SMOOTH THERMOPLASTIC LAYER ON THE ORDER OF .050 INCH THICK CONSISTING ESSENTIALLY OF A BINDER COMPRISING A HOMOGENEOUS BLEND OF 100 PARTS BY WEIGHT OF 10-60 PARTS OF READILY EXTENSIBLE WAXY, LOW DENSITY, SOLID BRANCHED THERMOPLASTIC ETHYLENE POLYMER, 5-75 PARTS OF SOFT, WEAK, FLEXIBLE RESILIENT ELASTOMER, 0-50 PARTS OF TOUGH, STRONG, FLEXIBLE ELASTOMER WHICH CAN BE FORMED INTO A SMOOTH SHEET, AND INSOLUBLE FINELY DIVIDED PARTICULATE FILLER, CONSTITUTING FROM ABOUT 1/20 TO ABOUT 2/3 THE VOLUME OF SAID LAYER, SAID FILLER FURTHER BEING PRESENT IN AMOUNT SUFFICIENT TO PERMIT SAID LAYER TO BREAK ING BUT INSUFFICIENT TO PERMIT SAID LAYER TO BREAK WHEN BENT BACK SHARPLY AGAINST ITSELF, AND 